Biodegradable free-standing nanomembranes of conducting polymer:polyester blends as bioactive platforms for tissue engineering

The present study reports the fabrication of free-standing nanomembranes with semiconducting and biodegradable properties. Nanomembranes have been prepared by spin-coating mixtures of a semiconducting polythiophene derivative, poly(3-thiophene methyl acetate), and a biodegradable polyester, poly(tetramethylene succinate). Both the roughness and thickness of the nanomembranes, which ranged from 3 to 20 nm and from 20 to 80 nm, respectively, were precisely controlled through the spin-coater speed and the solvent evaporation properties. Nanomembranes made of conducting polymer/polyester blends, which are able to retain the properties of the individual polymers, are stable in air and in ethanol solution for more than one year, facilitating their manipulation. Enzymatic degradation essays indicated that the ultra-thin films are biodegradable due to the presence of the aliphatic polyester. Interestingly, adhesion and proliferation assays with epithelial cells revealed that the behavior of the blend as cellular matrix is superior to that of the two individual polymers, validating the use of the nanomembranes as bioactive substrates for tissue regeneration.222585594MICINNFEDER [MAT2009-09138, MAT2009-11513]DIUE of the Generalitat de Catalunya [2009SGR925, 2009SGR1208, XRQTC]Euro Brazilian Windows agency [41309-EM-1-2008-PT-ERAMUNDUS-ECW-L16]FPU-UPCGeneralitat de CatalunyaFEDER [MAT2009-09138, MAT2009-11513]DIUE of the Generalitat de Catalunya [2009SGR925, 2009SGR1208, XRQTC]Euro Brazilian Windows agency [41309-EM-1-2008-PT-ERAMUNDUS-ECW-L16

Enhancement of the Electron Spin Resonance of Single-Walled Carbon Nanotubes by Oxygen Removal

We have observed a nearly fourfold increase in the electron spin resonance (ESR) signal from an ensemble of single-walled carbon nanotubes (SWCNTs) due to oxygen desorption. By performing temperature-dependent ESR spectroscopy both before and after thermal annealing, we found that the ESR in SWCNTs can be reversibly altered via the molecular oxygen content in the samples. Independent of the presence of adsorbed oxygen, a Curie-law (spin susceptibility $\propto 1/T$) is seen from $\sim$4 K to 300 K, indicating that the probed spins are finite-level species. For both the pre-annealed and post-annealed sample conditions, the ESR linewidth decreased as the temperature was increased, a phenomenon we identify as motional narrowing. From the temperature dependence of the linewidth, we extracted an estimate of the intertube hopping frequency; for both sample conditions, we found this hopping frequency to be $\sim$100 GHz. Since the spin hopping frequency changes only slightly when oxygen is desorbed, we conclude that only the spin susceptibility, not spin transport, is affected by the presence of physisorbed molecular oxygen in SWCNT ensembles. Surprisingly, no linewidth change is observed when the amount of oxygen in the SWCNT sample is altered, contrary to other carbonaceous systems and certain 1D conducting polymers. We hypothesize that physisorbed molecular oxygen acts as an acceptor ($p$-type), compensating the donor-like ($n$-type) defects that are responsible for the ESR signal in bulk SWCNTs.Comment: 14 pages, 7 figure

Fluid challenges in intensive care: the FENICE study A global inception cohort study

Fluid challenges (FCs) are one of the most commonly used therapies in critically ill patients and represent the cornerstone of hemodynamic management in intensive care units. There are clear benefits and harms from fluid therapy. Limited data on the indication, type, amount and rate of an FC in critically ill patients exist in the literature. The primary aim was to evaluate how physicians conduct FCs in terms of type, volume, and rate of given fluid; the secondary aim was to evaluate variables used to trigger an FC and to compare the proportion of patients receiving further fluid administration based on the response to the FC.This was an observational study conducted in ICUs around the world. Each participating unit entered a maximum of 20 patients with one FC.2213 patients were enrolled and analyzed in the study. The median [interquartile range] amount of fluid given during an FC was 500 ml (500-1000). The median time was 24 min (40-60 min), and the median rate of FC was 1000 [500-1333] ml/h. The main indication for FC was hypotension in 1211 (59 %, CI 57-61 %). In 43 % (CI 41-45 %) of the cases no hemodynamic variable was used. Static markers of preload were used in 785 of 2213 cases (36 %, CI 34-37 %). Dynamic indices of preload responsiveness were used in 483 of 2213 cases (22 %, CI 20-24 %). No safety variable for the FC was used in 72 % (CI 70-74 %) of the cases. There was no statistically significant difference in the proportion of patients who received further fluids after the FC between those with a positive, with an uncertain or with a negatively judged response.The current practice and evaluation of FC in critically ill patients are highly variable. Prediction of fluid responsiveness is not used routinely, safety limits are rarely used, and information from previous failed FCs is not always taken into account

Electron spin resonance on single-walled carbon nanotubes obtained from different sources

We used electron spin resonance (esr) to analyze several kinds of single-walled carbon nanotubes (swnts) synthesized by different methods. We observed that esr is a sensitive probe that can be used to observe major differences between samples of carbon nanotubes (cnts), in relation to their proportion of magnetic catalysts, impurities or defects. We analyzed the esr spectra of cnts in the usual way, by three overlapping lines. We then, implemented a function to fit the spectra, which gave us the intensity, line width (dhpp), and resonance line position (g factor) of each component line. The asymmetric line, which is assigned to the conduction electrons, could be used as a fingerprint of cnt purity. However, this asymmetric line is not always observed, since the three esr lines often overlap, particularly when there is a large amount of paramagnetic ions. We studied the esr spectra for different samples and estimated their purity by comparing the resulting parameters with data obtained by raman spectroscopy on the same samples

Plasma polymer thin films obtained by plasma polymerization of pyrrole

Thin films obtained by plasma polymerization of pyrrole were deposited on different substrates. The polymer films were obtained in a R.F. plasma polymerization reactor from low-pressure vapor of the pyrrole monomer. The R.F. power and gas pressure were adjusted to obtain optimal deposition rate and film adhesion to substrates. The film composition was determined using InfraRed Transmission and X-ray Photoelectron Spectroscopy (XPS)

Electron spin resonance study of single-walled carbon nanotubes

Studies of electron spin resonance (esr) are reported on several types of single-walled carbon nanotubes (swcnts) synthesized by different methods. We work both with the obtained samples, which contained randomly distributed semiconducting and metallic swcnts, and with selected 99% semiconducting or metallic swcnts. Our aim is to use esr spectroscopy in order to assess the quality of carbon nanotubes. We analyze the temperature dependence of esr spectra in the range 4–300?k and report the temperature dependence of the linewidth, the intensity and the asymmetry factor (i+/i-) of the esr lines. The esr response from the arc discharge swcnts produced using non-magnetic pt/rh catalyst and from the selected semiconducting tubes exhibits an asymmetric line with an intensity that remains almost constant with decreasing temperature, showing a constant linewidth of about 2.9?mt. For selected bucky paper (bp) metallic or semiconducting carbon nanotubes, we also study the esr signal according to the bp parallel or perpendicular orientation to the magnetic field. The g-factor and the asymmetry factor show a clear anisotropy